I have a 1991 Nissan 240sx, auto trans, hatchback (not that it matters) and this is what is happening:

I go to start up my car and everything is fine, it starts and it drives. But after driving for about 10 minutes the temp gauge goes up all the way. Now, the first time it happened I immediately pulled over and did all the normal checks and it cooled down. BUT is I continue to drive after it has gotten hot it will, after about 2-3 minutes, cool back down to normal.

1. Start car
2. 10 minutes or so it overheats
3. 2-3 minutes it cools back down
4. Everything is OK until the next time I drive it.
5. Rinse and repeat.

SO, the first thing I thought was thermostat. I took out the old thermostat and bought a new one, I then put them both on a wire in a pot of boiling water with an cooking thermometer to see when they opened. Both the new and the old opened at about 170 degrees Fahrenheit. exactly according to the service manual specs. I put the new one in and put everything back together. It still overheats in the same way.

NEXT, I thought I might as well check the water pump. It only costs about $35 so I pick up one from Advance Auto Parts and slap it in. No big deal. I take the car out for a drive, same problem.

FINALLY, I just decide to flush the system. My dad has one of those back flush kits and he lets me use it. I flush out the system thoroughly. Refill, and top off. I take it for a drive and everything is OK. I think HURRAY! But about a day later I get the same overheating issues.

So here I am: wondering what the problem is and running out of things to replace. I found a bottle of radiator cleaner in the garage, it is some sort of powerful cleaner that you run through the system and then drain out, anyways I will end up giving that a try.

But what do you guys think? Any ideas on what might be causing this?

 

are you completely bleeding the system?? raising the front of the car up etc???

 

after 10 min of driving the temp gauge going all the way up leads me to believe that you either have air in the coolant system or the temp sensor is faulty.

 

I have to admit, I probably haven't bled the system as well ad I shoulf have. I will bleed the system and post again. Thanks for the input.

 

i have the same exact problem
so far i have replaced
-upper radiator hose(hose gets squeezed up/air tight after overheating) but still doing the same
-theromostat, nismo lower temp one...doesnt help either...
-bleed the coolant properly all the time...doesnt help either

next up on my list is go pick up my new radiator cap from the dealer

 

that's disconcerting. Does anyone have a detailed step-by-step for bleeding the coolant system?

 

it's pretty much a matter of letting the car reach normal operating temp and opening the bleeder screw behind the p/s pump.

 

make sure your overflow is full so the air is displaced with water. there are several ways to bleed the car, the bleeder screw takes too long imo. make sure the thermostat isn't faulty. oftentimes air will sit right behind it and throw off the temp sensor reading.

 

care to elaborate?

 

+1


as for the "normal route"
take off radiator cap, loosen the bleeder screw, jack the car up or find a steep hill
start car, put on heat, full blast
wait until car heats up, thus thermostat opens up
just start pouring water in through the radiator, race the engine once or twice in between and keep the rpm at 2000 for 20 second while bleeding the system



i got lazy after my car constantly overheats, i just bleed the car without jacking the front up

 

My Cressida does this but it takes alot longer than 10 minutes and I dont have to turn the car off for it to cool down. Usually turning on the heater helps out alot. I'm thinking it's either my thermo or I'm just failing at flushing and bleeding the system.

 

I bled the system as best I could, and things have been OK since then. Hopefully that's all I needed to do.

 

if it comes back after couple weeks of driving or comes back after a day after using A/C....then its the same as mine...

 

I just had the same problem, replaces upper hose afer the leak, ran fine, then over heated, then replaced water pump.(this is at a shop a friend of mine ownes) said it was fixed, and again drocve fine for about 10min and then overheated, and shut down. When i took it back he said the head gasket is cashed. Hopefully it will help, but i still don't think thats the problem???????????

 

My buddy's S14 did the same thing...we flushed out the coolant, and we used a special funnel with a radiator cap attachment to completely bleed out the system without making a huge mess...we filled up the funnel about two thirds full, started up the car, and let it warm up. It took FOR-EVAR, but eventually sooo much air was bubbling out we thought he had a broken head gasket, but the bubbling subsided, and the problem went away...

Idk if you can get ur hands on such a funnel, but if you don't mind making a mess, just fill up to radiator, start it up with the cap OFF, and just sit and watch the pretty bubbles. It takes a long time though...it probably took more than 10 minuites of running the car to get the bubbles out, and make sure you top it off as bubbles come out....good luck